Sporeling stage

The nets that are seeded with the conchospores are stacked into bundles of four or up to 12-16 nets. These stacks of layered nets are transferred to the sea for nursery cultivation. In nursery culture, the nets are put into the sea and carefully monitored for blade development. During this early stage, the nets are raised out ofthe water daily to expose the young thalli to air and sun (nursery stage). This exposure is necessary to reduce fouling organisms (e.g., other seaweed species or microscopic algae such as diatoms). In Japan, a popular system, called the 'Ikada' system, is used for this process (Figure 1e). In China, Professor X. G. Fei has developed a floating A frame system that can be easily raised and lowered for support ing nursery nets and controlling the degree of exposure (Figure 1f). Once blades are 2-3 mm, the nets can be transferred to the farm sites or frozen for later use. These nets are initially air dried to reduce the water content of Porphyra to 20-40% and then are stored at -20 °C. The frozen nets can then be used to replace lost or damaged ones. When nursery reared seedlings are 5-30 mm in

Fixed pillar Semifloating raft All-floating raft

Three types of Porphyra cultivation

Three types of Porphyra cultivation

(c)

Semifloating raft

Mooring rope

Figure 2 (a) Three types of nori culture. (b) Cultivation methodologies for Porphyra: Determination of tidal level for cultivation. (c) Semifloating raft culture of Porphyra. (a) Modified from Tseng CK (1981) Marine phycoculture in China. Proceedings of the International Seaweed Symposium 10: 123-152. (b, c) Courtesy of X. G. Fei.

Mooring rope

Figure 2 (a) Three types of nori culture. (b) Cultivation methodologies for Porphyra: Determination of tidal level for cultivation. (c) Semifloating raft culture of Porphyra. (a) Modified from Tseng CK (1981) Marine phycoculture in China. Proceedings of the International Seaweed Symposium 10: 123-152. (b, c) Courtesy of X. G. Fei.

length, they are ready for out planting. Seedlings may be separated from the bundles using one of three methods of cultivation: fixed pole, semifloating raft, or floating raft (Figures 2a and 3a). The fixed pole method is used in shallow intertidal areas (Figure 2b). The floating type is designed for deeper waters. Specially designed harvesting boats lift the growing Porphyra nets (Figures 2a and 3b-3d). The semifloating raft is a hybrid ofthese two methods and is most suitable for areas that have extensive intertidal zones as at the mouth of the Yantzee River Estuary in China (Figure 2c and Figure 3a).

Harvesting and processing

The out planted Porphyra seedlings are allowed to grow to 15-30 cm in about 40-50 days before they are mechani cally harvested (Figures 3c and 3d). The remaining thalli are allowed to grow and may be ready for a second harvest after another 15-20 days. Several harvests may

be made from the same nets in one growing season as archeospores from the thalli reseed the nets during the growing season. Nets may be routinely harvested 6-8 times during the growing season (every 15-20 days), with yields of more than 3300 standard sheets (approxi mately 20 cm x 20 cm) per year.

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